Installation
34 A4774-1.0 HBM: public WTX110
Important
Terminal designation: Some manufacturers of components with RS485 ports
designate the terminals differently. According to the standard, the TxD+ / RxD+
port is designated 'B' and the TxD– / RxD– port 'A'.
Important
Cable: Always use twisted-pair cables! The surge impedance of the cable
should be approximately 150 W.
When laying cables for serial interfaces please note:
S Transfer lines connecting the serial ports must be installed so that inductive
and capacitive interference from other lines, machines or electrical devices
is ruled out. Interference on data transfer could result in delays or in the
program stopping.
S Self-wired cables must meet the following specification:
Shielded with twisted pairs, for example LIYCY 3 x 2 x 0.14 mm@ or LIYCY 3 x 2 x
0.25 mm@; shielded applied on both side
Cable resistance ≤ 125 Ω/km
Conductor cross-section ≥ 0.14 mm
2
to 200 m, ≥ 0.25 mm
2
to 1200 m
Line capacitance ≤ 130 nF/km
Cable length, RS232 max. 15 m
Cable length, RS485 max. 1200 m
Characteristic impedance of RS485 approx. 150 Ω
Nominal (rated) voltage of the cable ≥ 250 V
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